Wireless headsets and other portable communications devices are often battery powered such that a user can use the wireless headset or other such device without being directly connected to larger power source such as an a/c outlet or automobile battery. This allows wireless headset users flexibility and convenience to move about without being tied to a power cord. Wireless headset batteries are generally rechargeable so that the batteries can be recharged and need not be discarded after use.
In the prior art, devices employing rechargeable batteries typically have charging contacts so that charging current power can be supplied to recharge the batteries without removing the batteries from the device. In one typical setup, the portable device is inserted into a base charger which has spring loaded contacts that correspond to and couple with the contacts on the portable device. For example, such a setup is used with remote handset phones used in the home. The base charger is connected to a power source, and supplies charging current through the coupled contacts to recharge the batteries located within the device.
Spring-loaded wiping (surface) contacts are generally used with charging bases. This is a convenience feature as users can simply drop the portable device into a cradle without fumbling with a plug. Although there are plug-type docking connectors, such as those used by personal digital assistants (PDAs), there are several reasons why a plug connector is not a good solution when docking a headset to a base. The first is pull-out force. Plugs usually require too much force to connect and disconnect, requiring two hands to undock the headset, offsetting the main reason for the base in the first place: convenience. The second is that a plug connector does not lend itself to docking because of the wide variety of unknown future form factors.
Surface contacts can be placed on the side of a taper form headset or other portable rechargeable device, making docking into a cradle much easier than a plug. However, use of surface contacts and a charging base station with a headset rather than a plug present additional problems due to the smaller physical size and design of headsets. During the rechargeable device docking process, the formed ends of the base station charging contacts often come into contact with the plastic housing of the rechargeable device and can scratch the housing and pick up contamination which can cause intermittent electrical contact. One potential solution is to cut the rechargeable device housing away to fully expose the rechargeable device stationary contacts so that the spring loaded contacts of the base station never touched the plastic housing during docking. However, this solution may compromise the rechargeable device industrial design, aesthetics, and possibly weaken the rechargeable device structural integrity.
Furthermore, the headset or other rechargeable device may not be firmly detented with the charging base, which may also cause intermittent electrical contact. One potential solution to the weak coupling between the portable rechargeable device and charging base to dish the stationary contacts in the rechargeable device so that the rechargeable device detents when the ends of the spring loaded base station contacts press into the depressions in the rechargeable device contacts. However, this solution compromises the industrial design of the rechargeable device, and in addition the detent force is less than robust. Thus, improved charging interfaces between charging base stations and rechargeable devices are needed.